AJP - Regulatory, Integrative and Comparative Physiology, Vol 236, Issue 5 282-R291, Copyright © 1979 by American Physiological Society
Development of dependence on oxygen in embryo salamanders
E. F. Adolph
Survival times in anoxia and hypoxia were measured at various stages of
development in Ambystoma embryos and larvae of two species. Survival times
in anoxia at 20 degrees C shifted from more than 30 h at 2 days after
fertilization to 20 h at 10 days of age, to only 4--2 h at 14 days of age.
In hypoxia (oxygen pressure equivalent to 3.8% oxygen) similar shifts of
survival times appeared about 7 days of age later. During anoxia heart
rates decreased, less at younger stages than at older. At older stages the
heart stopped beating, sometimes irreversibly. In hypoxia also, hearts at
all stages whether in situ or isolated decreased their rates of beat.
Oxygen uptakes of larvae diminished in oxygen pressures even as high as 11%
oxygen. This critical oxygen pressure did not change between early stages
without blood flow and later stages with blood flow. Oxygen uptake was
probably not limited by oxygen delivery but presumably by properties of
cellular masses. No oxygen debts were paid off. Some parallel changes of
tolerances to anoxia in embryo birds and mammals are noted.
